1. Field of the Invention
This invention relates to measuring apparatus for determining the effective value of the power demand of an energy consumer over a period of calculation.
2. Description of the Prior Art
The suppliers of electrical energy endeavor to encourage the energy consumers to keep to a power demand which is constant with time. They therefore use tariffs which are composed of a portion which is dependent upon the energy taken, and a portion which is dependent upon the power.
It has been found that the effective value, or mean square value, of the power is highly suitable as a tariff value for determining the power-dependent portion.
The effective value Y.sub.eff or mean square value of a time-dependent parameter y is known to be defined as: ##EQU1## wherein T denotes the integration period and t denotes time.
For purposes of determining the effective value of the power demand of an energy consumer, the power may be continuously measured with a power measuring transducer, a signal which is proportional to the square of the power may be formed with a squaring means, the time integral of said signal may be formed with a capacitor, and finally the effective value of the power may be calculated from the time integral, in accordance with the formula set out above.
However, only if the effective value is determined over a comparatively short period of calculation can such a method supply measurement results which are of a satisfactory degree of accuracy